1. Field of the Invention
This invention relates to a micrometer, and a method for manufacturing cylindrical component for a micrometer. More specifically, it relates to a micrometer of which manufacturing cost and weight is reduced and a method for manufacturing an outer sleeve and a thimble used as components of the micrometer.
2. Description of the Related Art
As shown in FIG. 19, a micrometer comprises an almost U-shaped main body 101, an anvil 102 held at an end portion of the main body 101, a spindle 104 screwed into the other end portion of the main body 101 through an inner sleeve 103 to move toward and away from the anvil 102, an outer sleeve 105 placed and fixed onto the outside of the inner sleeve 103, a thimble 106 rotatably covered on the outside of the outer sleeve 105 and integrally connected with the spindle 104, and a ratchet mechanism 107 which slips when an excess load is applied on the spindle 104, and is provided at the rear end of the spindle 104.
On the outer circumferential surface of the outer sleeve 105, graduations 108A and numerals 108B of a main scale are formed at a predetermined pitch along the axial direction, and on the outer circumferential surface of the thimble 106, a graduation 109 of a vernier scale is formed at a predetermined pitch along the circumferential direction. By these graduations 108, 109, the amount of displacement of the spindle 104 to the anvil 102 can be measured. In other words, dimensions of the object which is held between the anvil 102 and the spindle 104 can be measured.
Conventionally, in forming the graduations 108A, 109A and numerals 108B, 109B, after the outlines of the graduations 108A, 109A and numerals 108B, 109B are formed by means of engraving or carving on the outer circumferential faces of the outer sleeve 105 and the thimble 106 fabricated in a predetermined cylinderical shape in advance, sumi ink is coated in the formed outlines, and then a baking treatment is carried out.
In the conventional forming method of the graduations 108A, 109A and numerals 108B, 109B, however, since the outlines of the graduations 108A, 109A and numerals 108B, 109B need to be carved or engraved one by one, considerable effort and time are required. Furthermore, after sumi ink is coated on portions formed by engraving or carving, the baking treatment is performed, so that the number of processes and costs are increased.
Since the outer sleeve 105 and the thimble 106 are conventionally formed of metal, they are heavy in weight and also bring up a disadvantage of spoiling the handling properties and operability, for a micrometer which to measure an object while holding it in one hand.
It is an object of the present invention to provide a micrometer which enables reduction in cost and weight.
It is another object of the present invention to provide manufacturing method of a cylindrical component for micrometer such as an anvil and a thimble which makes it possible to reduce the cost and the size.